Method and apparatus for direct detection, location, analysis, identification, and reporting of vegetation clearance violations

ABSTRACT

A method and system for processing digital image data taken from a three-dimensional topographic area including terrain and a right of way including a first and a second object to establish a clearance surface to define clearance violations within a boundary area. Waypoints are located to define a centerline and the boundary area to be analyzed. Vegetation coordinate points in the scene are determined from the digital image data. Ground coordinate points are determined from the digital image data. A clearance surface segment is constructed within the boundary area between the first and second object. The clearance surface is determined from the location of the first and second object and clearance criteria. The clearance surface is used to define a violation region.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of application Ser. No. 14/243,211filed Apr. 2, 2014, which has issued as U.S. Pat. No. 9,140,548 and is acontinuation of application Ser. No. 13/764,136 filed Feb. 11, 2013,which has issued as U.S. Pat. No. 8,724,900 and is a continuation ofapplication Ser. No. 12/844,500 filed Jul. 27, 2010, which has issued asU.S. Pat. No. 8,374,431, which are all incorporated by reference intheir entireties.

TECHNICAL FIELD

The present disclosure relates generally to the field of detecting,locating, analyzing, identifying, and reporting vegetation objectsand/or other objects (both natural and manmade) incorridors/rights-of-way to determine whether or not such objects violatespecific clearance criteria (clearance distance/spacing specifications)with respect to such objects' proximity (spatial relationship) tocritical operating components such as electric power conductors.

BACKGROUND

Aerial photography, light detection and ranging (“LIDAR”), syntheticaperture radar, and other types of remote sensing technologies arecapable of capturing digital imagery of real-world scenes for thepurpose of extracting three-dimensional point coordinate (spatialgeometry) data. These technologies are widely used in industry as vitaltools to collect the data necessary for map-making, engineeringmodeling, land management, vegetation assessment/management, and/orasset management. These tools are valuable because they can capturespatial (point coordinate) data in a digital form that ultimately allowsa wide variety of computer-based tools to be applied to the tasks ofmap-making, 3D modeling for engineering analysis, vegetationassessment/management, and/or asset management. Today, however,considerable time and effort (manual human intervention) is required to“interpret” the resulting imagery and extract information suitable(e.g., in a more meaningful object-oriented form) for theend-application use of the desired (necessary and sufficient)information. Thus, systems and methods are continuously sought toimprove the accuracy, effectiveness, and efficiency of “measurements”which can be directly compared or contrasted against specific criteriato determine the risks associated with any failures to meet/satisfy suchspecific measurement criteria.

Three-dimensional coordinate point data (3D imagery of a real-worldscene) is practically useless unless the location of individual pointsin 3D space can be compared to the locations of recognizable objectswithin the real-world scene (e.g., the relative spatial relationshipsbetween the recognizable objects and the individual measured points canbe compared to specific measurement criteria). The immediate need is todetermine whether or not specific clearance distances are maintainedbetween the recognizable objects and the individually measured points onthe potential violating object.

There are many tools available to model and analyze the spatialrelationships between two objects after they have been recognized andafter their geometric and physical attributes have been determined.However, at the present time, there are only a few rudimentaryapproaches (usually based on simple direct point-to-point distancemeasurements/calculations) to determine the degree of interference(relative spatial clearance criteria violation) between two objects in3D space.

The most widely accepted manual approach to dealing with vegetationclearance violations is to “clear-cut” the rights of way of all“significant” vegetation. This is also the most expensive and mostconservative approach, but it generally does away with the vegetationrisks within the boundaries of the rights of way. Outside the rights ofway, taller vegetation (trees) still pose a significant risk, andprotracted negotiations (often involving protracted court cases) withland owners are required to gain the right to mitigate such risks. Theissue of accuracy of the determination of the risk level is often thekey point of the negotiations.

Another widely accepted manual approach to identifying vegetationclearance violations of specific right of way clearance criteria is to:a) have an arborist or forester attempt to visualize where an electricalconductor or other object of interest might physically be/exist underspecific operating conditions; and then b) estimate and/or attempt tomeasure the distance from some vegetation point to an imagined point ona conductor or other object of interest where that particular conductorpoint might exist under a given operating condition such as conductoroperating temperature. Again, the issue of accuracy of the determinationof the risk level is often the key point.

One data intensive approach is to have photogrammetrists constructstereo-models from pairs of stereo photographs, either traditional filmor scanned digital images, of the right of way having objects ofinterest. Then, the photogrammetrists use their visual interpretiveskills to interpret the images and manually digitize (measure) thedistance between selected points on the recognized objects of interest.The measured distance is compared to the required clearance criteria toidentify violations. This is an interpretive approach subject to error.

Another data intensive approach is to have photogrammetrists and/or dataanalysts construct “point cloud” models from either stereo photographyor 3D LIDAR/synthetic aperture radar derived points, visually interpretthe point clouds, and digitize (measure) the distance between selectedpoints on the recognized objects of interest. Then the measured distanceis compared to the required clearance criteria to identify violations.Again, this is an interpretive approach subject to error.

Yet another data intensive approach is to have data analysts constructclassified “point cloud” models from 3D LIDAR/synthetic aperture radarderived points. This is done by subdividing or classifying the total setof available points into smaller sets of points with each set beingassociated with a particular object or type of object and then comparingeach point in one selected set of points with each point in each of theremaining sets of points to determine whether or not an interference(clearance violation) exists between any two points of the point setsbeing compared. The ability of the analyst to visualize the degree ofinterference (clearance violation) between any two interfering sets ofpoints is difficult at best; while the requirement to communicate thelocation and degree of interference to others is tedious, laborious, andnearly impossible to resolve, particularly when the possibility of verylarge numbers of clearance violations readily exists.

Yet another data intensive approach is to have data analysts/engineersconstruct classified “point cloud” models from 3D LIDAR/synthetic radarderived points (e.g., subdivide or classify the total set of availablepoints into smaller sets of points with each set being associated with aparticular object or type of object), construct engineering models fromthe data, construct the conductor catenary curves for the appropriateconductor operating conditions, and compare the distance from eachcatenary curve to each vegetation point to the required clearancecriteria in order to determine violations of the criteria usingautomated engineering analysis/design software packages. Although thisapproach produces accurate and useful results, it requires special 3Dengineering model construction and analysis skills to accomplish thetask.

Each of the preceding examples of existing available analyticalapproaches has at least one major shortcoming that has not been dealtwith to date. That is, not one of the previously mentioned approachesprovides the inspector in the field with a workable tool to accomplishhis job after the initial analysis results have been consumed (e.g., thevegetation violations have been cut or trimmed), and/or thevegetation/trees have grown back to a state that the violations havereoccurred. Thus, the capability to audit or check the clearing/cuttingwork or check for new violations does not exist.

Each of the preceding examples of existing available analyticalapproaches is directed toward the task of discerning the existence ofinterferences (clearance violations) between two recognizable objects ofinterest within the real-world scene of multiple available objects. Allof the above methods/approaches have major shortcomings; and few, if anyof the methods/approaches mentioned above, lend themselves to beingimplemented “in the field” or out in the physical real world where thephysical objects actually exist. The data processing events andcomputing power/equipment requirements of the previously mentionedapproaches prohibit such in the field execution of suchmethods/approaches. The data volumes are simply too large to handleeasily in the field. Meanwhile, manual methods require gross estimatesof changing physical conditions and accuracy is limited, so drasticsolutions such as clear-cutting prevail.

Thus there is a real need for a method/system and apparatus thatresolves the measurements/results accuracy and reporting issues as wellas the data volume issues while providing a solution approach that canbe applied equally as effectively in the office using more capable dataprocessing techniques and in the field using small, light weight,portable equipment.

SUMMARY

According to one example, a method for processing digital image datataken from a three-dimensional topographic area including terrain and aright of way including a first and a second object to establish aclearance surface to define clearance violations within a boundary area.Waypoints are located to define a centerline and the boundary area to beanalyzed. Vegetation coordinate points in the scene are determined fromthe digital image data. Ground coordinate points are determined from thedigital image data. A clearance surface segment is constructed withinthe boundary area between the first and second object. The clearancesurface segment is determined from the location of the first and secondobject and clearance criteria. The clearance surface segment is used todefine a violation region.

Another example is a portable device for analyzing whether an objectviolates a clearance criteria in an area. The device includes a laserrangefinder that determines the position of the object relative to theportable device via a single laser shot at the object. A position datainterface determines the position of the portable device. A storagedevice stores clearance surface data including a map of the area havingclearance surface boundaries. A controller determines the position ofthe object based on the position of the portable device obtained fromthe data interface and the position of the object relative to theportable device obtained from the laser rangefinder. The controllerdetermines whether the object violates clearance criteria.

Another example is a method of determining whether an object in an areaviolates a clearance surface. A map of the area including clearancesurface data is loaded on a mobile device. The position of the mobiledevice is determined electronically. The position of the object isdetermined via a single shot from a laser range finder to the object andthe determined position of the mobile device. The position of the objectis compared to the loaded map to determine whether the object is aviolation of the clearance surface.

Another example is a machine readable medium having stored thereoninstructions for producing a clearance surface in a region having afirst and second object in a right of way. The medium includes machineexecutable code which when executed by at least one machine, causes themachine to retrieve digital image data taken from a three-dimensionaltopographic image of the region, the region including terrain, the rightof way and the first and second objects. The code causes the machine tolocate waypoints to define a centerline and a boundary area to beanalyzed. The code causes the machine to determine vegetation coordinatepoints in the region from the digital image data. The code causes themachine to determine ground coordinate points from the digital imagedata. The code causes the machine to construct a clearance surfacesegment within the boundary area between the first and second object.The clearance surface is determined from the location of the first andsecond object and clearance criteria. The code causes the machine to usethe clearance surface to define a violation region.

Additional aspects will be apparent to those of ordinary skill in theart in view of the detailed description of various embodiments, which ismade with reference to the drawings, a brief description of which isprovided below.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an illustration of an unclassified LIDAR point cloud of anelectric power transmission line in its right of way area going througha forest for use by the disclosed method;

FIG. 2 is an illustration of an example of a classified LIDAR pointcloud of an electric power transmission line in its right of way areagoing through a populated area;

FIG. 3 is an illustration of the clearance surface(s) constructed withrespect to the right of way area and supporting structures/conductorsrelative to the coordinate point data that may be available;

FIG. 4A is an illustration of a cross-section of the clearance surfacetaken perpendicular to the right of way centerline of the electric powertransmission line shown in FIG. 3;

FIG. 4B is an illustration of the cross-section in FIG. 4A with theaddition of data points of a vegetation canopy;

FIG. 4C is an illustration of a cross-sections of three clearancesurfaces that were constructed similarly to represent three differentconductor operating conditions;

FIG. 4D is an illustration of the cross-sections in FIG. 4C with theaddition of data points of a vegetation canopy;

FIG. 5 is a graph illustrating the “radial” clearance surfaceconstruction process using radial clearance criteria;

FIG. 6 is a graph illustrating the “NESC” (National Electric SafetyCode) clearance surface construction process using NESC clearancecriteria;

FIG. 7 is a graph illustrating the clearance surface constructionprocess using a constant side slope angle procedure;

FIG. 8 is a perspective view of a handheld instrument that may use data,clearance surface models and analysis results obtained via the methodsdescribed herein;

FIG. 9A is a view of the display of the handheld instrument of FIG. 8showing a map with position data;

FIG. 9B is a view of the display of the handheld instrument of FIG. 8showing grow-in/fall-in violation analysis of a vegetation object;

FIG. 9C is a view of the display of the handheld instrument of FIG. 8showing the analysis of a vegetation object to determine allowableheight and/or side growth;

FIG. 9D is a view of the display of the handheld instrument of FIG. 8showing the criteria used to generate the analysis of the object in FIG.9B;

FIG. 10A is a scaled planimetric drawing of the results of a vegetationgrow-in/fall-in analysis using the clearance surface method showingvegetation violations;

FIG. 10B is a scaled planimetric drawing of the results of a vegetationheight/edge trimming analysis showing vegetation height violations;

FIG. 11 is an illustration of the “leaning tree problem;”

FIG. 12 is a flow diagram of the process to determine clearanceviolations; and

FIG. 13 is a block diagram of the components of the handheld instrumentin FIG. 8.

While these examples are susceptible of embodiment in many differentforms, there is shown in the drawings and will herein be described indetail preferred examples with the understanding that the presentdisclosure is to be considered as an exemplification and is not intendedto limit the broad aspect to the embodiments illustrated.

DETAILED DESCRIPTION

The present described process automatically produces a right of way mapwith clearance data. Generally the analytical process involved indetermining a vegetation violation includes transforming from apoint-to-point distance determination along with a comparison of thatpoint-to-point distance to a specific clearance distance criteria into aclearance surface solution for all possible locations at which aclearance violation could exist. The clearance surface, specific to aparticular conductor operating condition, divides three-dimensionalspace into a violation region and a non-violation region. It isdetermined whether or not a vegetation data point(s) exist either on theclearance surface or within the violation region (e.g., a violation). Amodel/data structure is provided along with an analysis capability thatsignificantly reduces the storage and computing power requirementsnecessary and sufficient to support the required analysis. A resultspresentation format is provided that significantly reduces the datavolume of the results while making the results easy to interface toexisting geographical information systems (GIS) datamanagement/presentation methods as well as interface with workscheduling mechanisms.

The analytical process involves using general industry-acceptedtechniques for defining right of way geometry. Waypoints are located todefine the centerline of a corridor (right of way) and its bounded areaof interest. Conductor catenary curves are determined (from classifiedLIDAR point clouds or some other appropriate means) to define thespatial location of points along the conductor(s) at one or morespecific operating conditions such as temperatures. Vegetationcoordinate points are determined from classified LIDAR point clouds orsome other appropriate means and stored for subsequent assessment. Bareearth or ground coordinate points are determined from classified LIDARpoint clouds and stored for subsequent analysis.

Three-dimensional, edge-matched clearance surface segments areconstructed for each specific conductor operating condition/temperatureof interest, to define spatial regions which could contain coordinatepoints which either represent clearance violations or do not representclearance violations. The constructed clearance surface(s) are segmented(based on centerline and right of way boundary definitions) tofacilitate efficient data storage and access. The bare earth coordinatepoint data are segmented (based on centerline and right of way boundarydefinitions) to facilitate efficient data storage and access. Thesegmented clearance surface(s) are used to analyze each availablevegetation point and determine whether or not each specific vegetationpoint violates the specific clearance criteria for the conductoroperating condition being analyzed. The analysis results which areviolations are “clustered” to reduce data volume while preserving theidentity/location of the violating vegetation/trees. The segmentedclearance surface(s), analysis results, and bare earth data (the datamodel contents) are transferred to a handheld computing device via adata storage card for example. The handheld computing device is used forperforming the inspection/analysis in the field such as on-the-spot atwhich new measurements are taken.

The specific aspects of the above mentioned method with respect todetermining violations of a right of way will be discussed in detailwith regards to FIGS. 1-7. FIG. 1 is an illustration of an unclassifiedLIDAR point cloud (point coordinates) of an electric power transmissionline 102 in its right of way area going through a forest 104. Thedifferent colors 106, 108, 110, 112, 114, 116 and 118 in FIG. 1 depictonly the elevations-above-sea level of each individual LIDAR point inthe point cloud. The elevations are color coded such that points atlower elevation are colored violet 106 while the points at the highestelevation are colored red 116. In this example, the colors of thespectrum, violet 106, indigo (not shown), blue 108, green 110, yellow112, orange 114, and red 116 are used to indicate elevation. At thispoint in the data processing scheme, each of the individual LIDAR pointsdefines a point in three-dimensional space (x, y, z), but no singlepoint has been associated with the “named” or type of object it belongsto and therefore each points remains unclassified. Before any type ofanalysis can be accomplished using this type of point coordinate data,each point in the point cloud must be classified according to the typeof object the particular point is a part of.

FIG. 2 is an example of a classified LIDAR point cloud (pointcoordinates) of an electric power transmission conductor 202 in itsright of way area 204 going through a populated area. At this point inthe data processing scheme, each of the individual LIDAR points definesa point in three-dimensional space (x, y, z); and each individual pointhas been associated with the “named” object to which it belongs. In thisexample, the white colored points 206 belong to objects classified as“vegetation,” the red colored points 208 belong to objects classified as“rooftops,” the bright green colored points 210 belong to objectsclassified as “electric power transmission facilities,” and the darkergreen colored points 212 belong to objects classified as grasses (veryclose to the ground) and the darker maroon colored points 214 belong toobjects classified as “terrain” or “bare earth.”

A point's classification determines: a) how it will be treated relativeto each other point; and b) what clearance criteria should be applied.For instance, a point location that is classified as a vegetation pointlocation 206 can be compared spatially with one or more point locationsthat are classified as a conductor point location 202 (or vice versa) inorder to determine whether or not the vegetation point location poses athreat to the conductor's point location based on the required clearancerequirement that must be maintained. Comparing the location of onevegetation point location with another vegetation point location is notof interest in this analysis. Determining the spatial relationshipbetween vegetation point locations and ground/bare earth point locationsare necessary to determine the height above ground of the particularvegetation point of interest. Additionally, even houses, fences, otherpower poles, and even the ground may pose a threat to the integrity ofthe operation of the electrical conductor 202 under certain conductoroperating conditions. Thus, determining whether or not a point in spaceviolates the clearance criteria for the electrical conductor undervarious conductor operating conditions is of interest.

FIG. 3 shows an example of coordinate point cloud data, which in thisexample is airborne LIDAR data that was captured along a specific rightof way 302 along with a constructed clearance surface or surfaces 304.In FIG. 3, the coordinate point cloud data has been classified intospecific object categories including structures 322 and a conductor 306for an electric power transmission line, bare earth or ground datapoints 308 representing the terrain, and vegetation 310 includinggrasses/weeds, brush, and trees. Other manmade structures(obstructions/encroachments) are often found within the coordinate pointcloud. These manmade structures could be considered to be violations ofany specific conductor clearance criteria being analyzed/applied totheir classification.

As shown in FIG. 3, the clearance surfaces relate directly to theelectrical conductors and associated supporting structures. In thisexample, there is one clearance surface per span. As such, the clearancesurface(s) 304 represent a semi-permanent asset of the owner. Thus theclearance surface or surfaces may be used and re-used well into thefuture until either the geometry or the operating conditions of theconductor are changed. The clearance surface(s) is constructed based onthe geometry of the conductors and the specific vegetation clearancecriteria but not on the spatial relationship with the surroundingvegetation data points.

Since the clearance surface is constructed using the geometry of theelectrical conductor 306 at a specific conductor operating condition andthe specified clearance criteria (depending on point classification),the unique clearance surface will remain as a semi-permanent asset aslong as the physical geometry of conductor attachment points (on thesupporting structure) is not changed, the conductor operatingtemperature(s) being analyzed are not changed, and the clearancecriteria (for a particular point classification of interest) are notchanged. However, construction of clearance surfaces for thedetermination of violations of vegetation clearance criteria is ofinterest even though the same approach would be taken to construct otherclearance surfaces for other classifications of object coordinate pointsusing conductor clearance criteria unique and particular to such otherobject point classifications.

The clearance surface is constructed uniquely for each span in thisexample. The span is the right of way area between two consecutivestructures that support the electrical conductors 306, such as latticetowers 320 and 322 in FIG. 3. The clearance surface may be extended outbeyond the boundary of the right of way as far as necessary to take intoaccount taller (hazard) trees that could fall into the right of way andthreaten the integrity of the electrical conductors 306. The clearancesurfaces are constructed to follow the catenary shape of the electricalconductors 306 and whatever the conductor operating condition (operatingtemperature) to be analyzed. Multiple conductor operating conditions maybe considered for a single analysis. These conductor operatingconditions may include the condition “as flown” or “as measured” or “asinspected.” The operating conditions may also include the sag or blowoutof the conductor 306 at maximum operating temperature and/or maximumwind/blowout conditions.

The clearance surface(s) effectively divide space into contiguous,seamless regions containing coordinate points that either violate theconductor clearance criteria or do not violate the conductor clearancecriteria. Therefore, the construction of the clearance surface is notdependent on its relative proximity to either the vegetation coordinatepoints or to coordinate points on manmade objects either inside oroutside the rights-of-way. The clearance surface represents thecollection of all points in space that just barely violate the conductorclearance criteria. Therefore, all vegetation coordinate points (ormanmade object coordinate points) that lie on the clearance surface orare above the clearance surface are coordinate points that violate thespecific conductor clearance criteria being analyzed. The clearancesurface is a seamless surface that is constructed along the shape of thesagging conductor 306 at one or more conductor operating temperatures orconditions in this example. The conductor operating condition may takeinto account the wind loading, ice loading, solar heating, andelectrical loading of the conductor 306 as may be applicable to theparticular analysis/investigation of interest. It is practical anddesirable to analyze multiple conductor operating conditions andmultiple conductor clearance criteria concurrently.

The outward expanse of the clearance surface construction, expressed asthe distance from the right of way centerline, is necessary to determinewhether or not a vegetation coordinate point or a coordinate point on amanmade object represents a conductor clearance violation. The point'sheight above ground is of interest, because taller objects can fallfarther in a direction toward the electrical conductor. Theextension/expanse of the clearance surface construction outward from thecenterline may be different at the structure locations and at the pointof maximum conductor sag. The risk of vegetation clearance violation maybe considered to be less in the vicinity of the structure with a higherelevated point than it might be at the location of maximum conductor sagwhich generally is located near the middle of a span. However, thislevel of risk assessment is determined by a user. Often, the clearancesurface will be extended farther at the “mid-span” location of maximumconductor sag and less at the structure location as shown in FIG. 3.

Since it is easier for a forester to estimate the height of an objectabove the ground rather than to estimate an object's elevation above sealevel, the bare earth coordinate data plays an important role in thepresentation of the clearance surface construction results. The finalpresentation of the clearance surface results depicts the clearancesurface(s) in terms of their height above ground at all clearanceviolation locations above the right of way.

FIG. 4A is an illustration of a cross-section of a clearance surface 400taken perpendicular to the right of way centerline or alignment of anelectric power transmission line 306 shown in FIG. 3. FIG. 4A shows thepositions of three primary conductors 402, 404 and 406 of the electricpower transmission line 306 at the time the data was captured (e.g., theas flown or as measured conductor operating condition/temperature). Thearea directly under the three conductors 402, 404 and 406 is termed awire zone 410. Two border zones 412 and 414 extend beyond the wire zone410 on either side. The border zones 412 and 414 extend out to or towardthe boundary of the right of way. The boundary of the right of way isnot shown discretely in FIG. 4A, because the right of way boundarylocation itself is not important to the construction of the clearancesurface except to the extent that the clearance surface needs to extendbeyond that boundary. Tall objects such as trees grow beyond theboundary of the right of way, and some of these taller objects/trees maypresent a threat to the power line. The conductor configuration ishorizontal for the single circuit electric power transmission line 306.In this example, the right of way is symmetrical, in the plan view,about a right of way centerline 420. It is to be understood that theright of way does not have to be symmetrical in order to utilize thedescribed process.

The clearance surface cross-section in this example is represented by aline 400 which divides the chart into a violations region 432 containingvegetation points that represent violations of the radial clearancecriteria and a non-violations region 434 containing vegetation datapoints that represent non-violations of the radial clearance criteria. Across-section of the ground or bare earth surface 436 is shown in FIG.4A, because tall objects such as trees stand on the ground. When tallobjects fall in the direction of the power lines, the falling objectspivot about some point on the ground and this affects the shape of thecalculated points on the clearance surface. Coordinate points that lieon or above the cross-section of the clearance surface 400 representviolations of the radial clearance criteria. A tall object or treereaching a height-above-ground equal to or greater than the height aboveground of the clearance surface 400 would, if it fell, violate theradial clearance criteria. Optionally, the lifting/thrusting effect ofthe rootball of the falling tree may or may not be taken into accountduring the execution of the analysis.

In this example, the units of measure are the US Survey Foot in FIG. 4A.The clearance surface geometric modeling concept is equally suited totransmission line construction techniques featuring multiple circuits,vertical conductor configurations, right of way layout configurationsthat are not symmetric about the right of way centerline 420, and othervariations.

When constructing the clearance surface, it is convenient to constructthree components of the continuous clearance surface for a single span.A span is the area contained within the boundaries of the right of waybetween two consecutive supporting structures. The span's conductorshang (sag) between the supporting structures, and the conductors runessentially parallel to the centerline. The continuous clearance surfaceis a gridded surface constructed in parallel cross-sectionsperpendicular to the centerline in this example, but other constructionsmay be used. The grid spacing can be varied, but a 2 foot to 3 foot gridcell size is completely sufficient for the intended analysis ofvegetation point cloud data.

The three component surfaces that compose the span's clearance surfaceare associated with the wire zone 410, the left-side border zone 414,and the right-side border zone 412. The wire zone clearance surfacecomponent is constructed as a grid bounded by the outermost conductors,in the case of a horizontal conductor configuration using a radialclearance criteria. Each of the border zone clearance components isedge-matched to the wire zone surface component. If desired, ahorizontal safety distance could be added to extend the wire zone, theborder zone or both.

To construct the surface components, the process starts at a structureand proceeds by constructing one surface cross-section at a time,proceeding from the starting structure to the ending structure of thespan. At the starting structure, the wire zone cross-section componentis created by placing equally spaced grid points along a line betweencorresponding points of the two outermost conductor catenary curves.Thus, the surface cross-section is essentially perpendicular to theright of way centerline 420. To account for turns along the centerline,the bisecting angle of the turn becomes the cross-section alignment atthe starting structure, and the surface's cross-sectional alignment isincrementally rotated for successive cross-sections until the surfacecross-sectional alignment becomes parallel to the bisecting angle of theturn at the opposite end of the span (at the span's ending structurelocation). Of course, when no turns are encountered for several spans,the clearance surface's cross-sectional alignment is perpendicular tothe centerline 420.

The clearance surface construction process proceeds from the beginningto the ending structure in the span in equal incremental steps along thecenterline 420. At each successive incremental step along the centerline420, the wire zone surface component, the left-side border zonecomponent, and the right-side border zone component are constructed ascross-sections of equally spaced grid points. As surface grid lines areadded along the centerline, the elevation (or sag) of the conductor'scatenary curves (dependent on conductor operating temperature) controlsthe shape of the clearance surface; and as steps are taken along thesurface cross-section (e.g., boundary to boundary and beyond), theground surface and the clearance criteria combine to influence the shapeof the cross-sectional line of grid points. Thus, the completedclearance surface is a three-dimensional delimiting surface between twospatial regions, the violations region 432 that includes vegetationclearance criteria violations and the non-violations region 434 thatdoes not contain vegetation clearance criteria violations. Vegetationpoints that lie on the clearance surface are defined as violations ofthe clearance criteria. Thus, the clearance surface embodies thecomplete geometry of the conductors (the asset to be protected) while italso contains the information necessary and sufficient to analyze eachand every vegetation point that could present a threat to the protectedasset. The clearance surface is the solution of all possible violationsof the clearance criteria as applied to the three-dimensional space ofthe right of way or corridor.

FIG. 4B is the same illustration as FIG. 4A, with the addition of across-section of a vegetation canopy 440. As may be seen in FIG. 4B, across section of a trees canopy 442 on the left side is shorter than atree canopy 444 on the right side. The points on the tree canopy 444that are above the clearance surface 400 represent points on a tree suchthat if that tree fell toward the conductors, the points would violatethe radial clearance criteria, assuming that the pivot point were on theground surface directly below the point of interest. Since not all“falling” points are positioned directly above the pivot point of afalling tree, this analysis presents a conservative, yet typical andeffective approach to the analysis of the point cloud data.

The efficiency of the clearance surface model is illustrated as follows:Vegetation points that lie on or above the clearance surface 400 such ascertain of the tree canopy 444 are violations of the clearance criteriawhile points that lie below the clearance surface 400 are not violationsof the clearance criteria. Thus, the analysis approach is simplified tothe determination of the signed elevation difference between avegetation point as it exists in three-dimensional space and its closestinterpolated neighbor point on the clearance surface.

FIG. 4C is a cross section view of three clearance surfaces that wereconstructed similarly (e.g., using the same radial clearance criteria)to represent three different conductor operating conditions. Likeelements in FIG. 4C are labeled with like element numbers as in FIGS.4A-4B. A first line 450 represents the as flown/as measured operatingcondition/temperature as shown in FIGS. 4A-4B. A second line 452 is themax-blowout operating condition which has a different conductoroperating temperature along with a lateral wind loading that “blows out”the conductor or causes the conductor to “swing out in the wind.” Athird line 454 represents the maximum sag operating condition whichcorresponds to the maximum anticipated conductor operating temperature.

All three of the clearance surfaces shown in FIG. 4C are constructed inthe same fashion except that the “blown-out” region of the max blowoutsurface 454 is uniquely constructed, taking into account the length ofthe insulator and whether or not the insulator is or is not constrainedfrom swinging. The blown-out region of the surface defines the entirebounding envelope of the conductor as it swings out due to the windloading. The blown-out region of the surface is a continuous griddedsurface segment of the clearance surface border zone component. In thisexample, the conductor operating temperatures chosen to illustrate thedifferent shapes of the clearance surfaces for the three different namedconductor operating conditions were chosen for convenience of dealingwith the named surfaces in a particular order (e.g., as flown/asmeasured, maximum blowout, and maximum sag) and these operatingtemperatures do not necessarily represent specific real-world conditions(e.g., a high wind would actually cool the conductor down, perhaps to atemperature below that of the as flown/as measured condition). That is,the maximum blowout clearance maintains the clearance criteria but islower than the as flown/as measured clearance surface because of theincreased conductor sag of the maximum blowout due to a higher conductoroperating temperature, and so the relative spatial relationship betweenthe maximum blowout clearance surface and the maximum sag clearancesurface.

FIG. 4D is an illustration adding a cross-section of a vegetation canopy460 to the illustration in FIG. 4C. On the left side of FIG. 4D, thetrees canopy of the vegetation canopy 460 is shorter than the treecanopy of the vegetation on the right side 460. Again, the efficiency ofeach clearance surface model is illustrated in this example. Vegetationpoints that lie on or above the applicable clearance surface 450, 452 or454 are violations of the clearance criteria while points that lie belowthe applicable clearance surface are not violations of the clearancecriteria. Thus, the analysis approach is simplified to the determinationof the signed elevation difference between a vegetation point as itexists in three-dimensional space and its “closest” interpolatedneighbor point on the clearance surface.

FIG. 5 illustrates the “radial” clearance surface construction processusing radial clearance criteria. Similar to FIG. 4A, the cross-sectionin FIG. 5 includes a wire zone 500 with conductors 502 which arecentered around a right of way centerline 504. A line 506 represents theclearance surface. The clearance surface for each span will beconstructed for each conductor operating condition (temperature) beingmodeled and subsequently analyzed. Before the clearance surface(s) canbe constructed, the following geometric and spatial data must beknown: 1) radial clearance criteria for each conductor operatingcondition (temperature) to be analyzed; 2) ground surface or digitalterrain model; and 3) catenary curves describing the geometry (locationof discreet points) of the conductor(s) for each span along the entirelength of the right of way to be modeled.

A critical part of the method of constructing the clearance surface 506is the determination of its height (directly above the location of thebase of the tree on the ground) at which a tree is found to be aviolation of the clearance criteria. That is, the use of the method todetermine the location of the vegetation's minimum “allowable” heightabove ground not only locates a point on the clearance surface 506, butalso it identifies the location of the vegetation violation. Thisapplies for the radial clearance criteria as well as for the NESCclearance criteria.

The surface construction process begins with the construction of a“border zone” extension 508 of the clearance surface for one of the mostoutboard conductors for a single span located at the beginning end ofthe right of way to be modeled (e.g., starting station distance alongthe centerline is equal to zero). A working catenary point isestablished by starting at the first (behind) structure location (on thecenterline) and moving in a direction perpendicular to the centerline504 outboard to a point (Point #1) which represents a point on the mostoutboard conductor. Assuming a suspension insulator, this conductorattachment point is located on the conductor catenary curve. Point #1 isnow the working catenary point. A second point (Point #2) is establishedon the ground surface cross-section directly below Point #1. Point #2 isnow the working ground surface cross-section point. Point #2 representsthe base of a falling tree. Successive clearance surface points areconstructed directly above ground surface cross-section points movingrepeatedly (in equally spaced steps) out along the ground surfacecross-section.

A third point (Point #3) is established on the ground surfacecross-section by moving from Point #2 (base of a falling tree) backalong the ground surface cross-section toward the centerline 504 ahorizontal distance equal to the rootball radius (r) of the fallingtree. Point #3 represents the pivot point about which the falling treewill rotate if and when it falls toward the conductors 502. The groundelevation at the base of the falling tree (Point #2) will likely beabove or below the elevation of the pivot point (Point #3) of thefalling tree, located at the edge of the rootball because the groundcannot be assumed to be level. The elevation difference between Point #2and Point #3 is determined asE=(Elevation of Point #3)−(Elevation of Point #2), a signed value

A vector V13 is established between Points 1 and 3 as V13=P1P3 in thisexample. The magnitude of vector V13 is computed. L is assigned |V13|. Apoint (Point #4) is established on the vector V13 at a distance (fromPoint #1) equal to one half the magnitude of vector V13. d is assignedas |V13|/2=L/2. Point #4 will be used as a center construction point fora circle of radius R, where R=L/2.d=(L/2)=R

At Point #3, a circle of radius r is constructed where r=(rootballradius). In this example, this circle does not pass through Point #2(base of the falling tree) due to the ground slope at the base of thetree. However, this circle (radius of r) does pass through a point whichdivides the chord of a larger circle (through Point #2) of radius r′into two equal parts of length E. The base of the falling tree lies onthis larger circle of radius r′. The radius (r′) of the larger circle isdetermined to be: r′=(r/cos(theta)), where theta=A TAN 2(E/r).

The radius (r′) of the larger circle is of no significance to thesurface construction method other than to make note that the horizontalline passing through the pivot point (Point #3) bisects the chord of thelarger circle at a horizontal (radial) distance equal to r (thehorizontal rootball radius). However, it is significant that theintersection point of the horizontal line through Point #3 and the chordof the larger circle will rotate counterclockwise about Point #3 to aPoint #7 as the tree falls toward the conductor Point #1. The fallingtree aligns to the line between Point #1 and Point #7, the line beingthe tangent line from Point #1 (the conductor) to the boundary of thesmaller circle of radius r, the tangent point being Point #7.

The circle (radius R) centered at Point #4 is intersected with thecircle (radius r) centered at Point #3 to locate the two intersectionpoints that define the chord of the circle (radius r) centered at Point#3. The chord is the line between the two intersection points of the twointersecting circles. The length (and as such the half-length) of thischord is determined as follows:X ² +Y ² =R ² circle centered at Point #4  (1)(X−d)² +Y ² =r ² circle centered at Point #3  (2)The terms of equations (1) and (2) are combined.(X−d)²+(R ² −X ²)=r ²  (3)X ²−2dX+d ² −X ² =r ² −R ²  (4)X is solved for.X=(d ² −r ² +R ²)/(2d)  (5)From equation (1),Y ² =R ² −X ² =R ²−[(d ² −r ² +R ²)/(2d)]²  (6)Y=[(4d ² R ²)−(d ² −r ² +R ²)²]/(4d ²)  (7)Where Y is half the chord length and the entire chord length (a) isequal toa=(1/d)[(4d ² R ²)−(d ² −r ² +R ²)²]^(1/2)  (8)a=(1/d)[(−d+r−R)(−d−r+R)(−d+r+R)(d+r+R)]^(1/2)  (9)Substituting for d (since d=R) results ina=(1/R)[(r ²−4R ²)(r ²)]^(1/2)  (10)A distance (D₁) is defined from Point #1 to Point #8, where Point #8 islocated at the intersection of vector V13 and the chord of the circlecentered at Point #3.D ₁=(L/2)+X  (11)A distance (D₂) is defined from Point #1 to Point #7 where Point #7 isan intersection point of the two circles constructed earlier.D ₂ =[D ₁ ² +Y ²]^(1/2)  (12)A distance from Point #1 is defined to the base of the falling tree.D ₃ =D ₂ +E  (13)The minimum height (H) of a falling tree located at Point #2 that willjust fail to meet the specified clearance criteria (C) is defined as:H=D ₃ −C=((D ₁ ² +Y ²)^(1/2) +E)−C  (14)A Point #6 is established as a point on the clearance surfacecross-section) at a height-above-ground (directly above Point #2).

The analysis continues to move outward from the centerline 504 in smallequal incremental distances along the ground surface cross-section andcontinue to define points of the clearance surface cross-section. Theanalysis continues to move outward beyond the right of way or wire zoneboundary 500 until a distance has been traversed sufficient to mitigatethe threat of the tallest tree anticipated to exist along the edge ofthe right of way boundary. The above steps are repeated until the nextconsecutive structure is reached to complete the construction of theclearance surface component for the border zone of interest and beyondthe right of way boundary.

The above steps are then repeated for the border zone region of theopposite side of the centerline 504. The clearance surface componentwithin the wire zone 500 is constructed by constructing a grid of pointsbetween corresponding points on the two outermost conductor catenarycurves while taking into account the “falling tree effect” as was doneusing the intersecting circle technique during the construction of theBorder Zone clearance surface components. Clearance surfaces areconstructed for each consecutive span in the entire line segment beingmodeled.

The mathematical treatment presented above applies to the radialclearance criteria. Another generally accepted type of clearancecriteria is the NESC (National Electric Safety Code) criteria. Whereasthe radial clearance criteria has only a radial component, the NESCcriteria has both a horizontal and a vertical component (e.g., theviolation zone is a box rather than a radial distance). The techniquesfor constructing the clearance surfaces using the NESC clearancecriteria remain essentially the same as the techniques for using theradial criteria except for the determination of the value of H inequation 12. Thus, the value and usefulness of the clearance surfaceconstruction technique is extended to the use of the NESC clearancecriteria as well.

FIG. 6 is a graph illustrating the “NESC” (National Electric SafetyCode) clearance surface construction process using NESC clearancecriteria. A NESC clearance surface for each span will be constructed foreach conductor operating condition (temperature) to be modeled andsubsequently analyzed, just as is the case for the radial clearancecriteria. Before the NESC clearance surface(s) can be constructed, thefollowing geometric and spatial data must be known: 1) NESC clearancecriteria for each conductor operating condition (temperature) to beanalyzed; 2) ground surface or digital terrain model; and 3) catenarycurves describing the geometry (location of discreet points) of theconductor(s) for each span (e.g., the right of way area betweenconsecutive supporting structures) along the entire length of the rightof way to be modeled.

The description of the surface construction process using the NESCclearance criteria is identical to the process for constructing theclearance surface(s) using radial clearance criteria in FIG. 5 aboveexcept for the determination of the value of the variable C as used inequation (12) to determine the height above ground for a correspondingpoint on the clearance surface. Since the NESC clearance criteriaconsists of both a horizontal and a vertical component, the value of theresultant clearance criteria C must be derived using both components.

Prerequisites for constructing the NESC clearance surface include a)determining the location of Point #5 and b) determining the location ofPoint #7, as shown in both FIGS. 5 and 6. The location of Point #7 isnot a requirement for the construction of the radial clearance surface.

First Point #5 is located on either the horizontal or vertical boundaryof an NESC clearance “box” depending on the location of Point #2. AfterPoint #5 is located, a vector V15 is constructed from Point #1 to Point#5 and the magnitude of vector V15 is computed to determine the value ofC. Now, the value of H is computed as specified in equation (12). Thedetermination of the location of Point #5 proceeds as follows.

A horizontal unit vector v_(c) directed outward from the workingcatenary point and in the vertical plane of the ground/surfacecross-section. A vertical unit vector k is defined parallel to thez-axis. A unit vector v_(p) is defined perpendicular to the verticalplane containing both the clearance surface cross-section and the groundcross-section while pointing in the general direction of increasingstation distance along the span's centerline.v _(p)=(−v ₁)×(+k), vector cross product of the unit vectors v ₁ andk.  (15)A vector V₅=P8P7 is defined and a unit vector v₅=V₅/|V₅| is defined,wherev ₅ =v _(p)×(−v ₁), vector cross product  (16)V ₅=[(Y)v ₅]=[(a/2)v ₅]  (17)Point #7 is defined as P ₇ =P ₈ +V ₅  (18)Vector V ₆ is defined as V ₆ =P1P7, and unit vector v ₆ =V ₆ /|V₆|  (19)The angle “theta” is defined where w is defined as the length of thediagonal of the NESC clearance criteria box, or w=(h ² +v ²)^(1/2)  (20)(theta)=cos⁻¹(h/w)  (21)The angle “beta” is defined as(beta)=cos⁻¹[(v ₆)·(−k)], the dotproduct  (22)The angle “alpha” is defined as(alpha)=90−(beta)  (23)If alpha>theta, |V ₇ |=v/[cos(beta)]=C  (24)If alpha<theta, |V ₇ |=h/[cos(alpha)]=C  (25)P ₅ =P ₁ +|V ₇ |v ₆, and  (26)The minimum tree height above the ground to the NESC clearance surfaceis defined asH=(|V ₆ |+E)−C  (27)Thus, different types of clearance criteria are used in the constructionof the clearance surface.

FIG. 7 illustrates the construction of the clearance surface using avertical clearance criteria to establish the clearance surface in thewire zone and a constant slope angle (measured from the horizontal) forthe construction of the clearance surfaces in the border zones.Additionally, a horizontal “safety” distance has been applied to extendthe wire zone clearance surface horizontally outward from thecenterline. FIG. 7 includes lines 702, 704 and 706 that each illustratethe conductor positions for three conductor operating conditions. Inthis example, the operating conditions are as flown/as measured, maximumblowout and maximum sag. FIG. 7 also shows lines 712, 714 and 716representing the clearance surface cross-sections for the clearancesurfaces constructed for each of the conductor operating conditions.

The constant angle construction of the clearance surface extendingoutward through the border zone and beyond the right of way boundary isa technique intended to make it quite easy for the field inspector tovisualize whether or not a tree will violate the specified clearancecriteria or not. This approach illustrates creating a clearance surfacethat delimits the space in the right of way into regions that do containviolations of the clearance criteria and regions that do not containviolations of the clearance criteria.

The data obtained through the above analysis may be utilized by ahandheld field inspection device 800 shown in FIG. 8. As shown in FIG.8, the fully integrated handheld device 800 includes a non-magneticstaff 802 for conveniently attaching the various components of thehandheld device 800. The device 800 includes a GPS antenna 804, a laserrange finder 806, a handheld computer 808 and a detachable laser pointer810. The handheld computer 808 includes a display screen 812. Oneexample process involves taking a single measurement using a single-shotfrom the integrated laser range-finder 806 to determine the remotespatial (GPS) location of a potential violating vegetation point. Thepotential violating vegetation point is analyzed using software todetermine whether or not the located vegetation point is or is not aviolation based on the specified clearance criteria. The softwareaccesses the stored clearance surface models to enable local processingby the integrated handheld computer 808 mounted on the device 800. The“pass (No Violation)/fail (Violation)” status of the captured/locatedvegetation point is presented using the display 812 of the integratedhandheld computer 808 mounted on the non-magnetic staff 802. Thegeographic location of the failing (violation) vegetation point isplotted as a symbol on the graphics display screen 812 of the integratedhandheld computer 808. The graphics display screen presents all capturedvegetation points (failing and non-failing) in the form of a geographicmap which also displays the GPS location of the user and handheld device800 along with the centerline of the corridor/right of way, the right ofway boundaries, structure locations within the right of way, and allvegetation violations that are known from earlier/previous analyses.

Upon return from the field inspection the vegetation points whichrepresent clearance violations are downloaded, in both text andGIS/shape-file electronic format, to more permanent data storagefacilities for further processing in an office environment. The fieldanalysis results are transferred to a more permanent form of datastorage for future use. These results may include the segmentedclearance surface(s), the bare earth data, and information pertinent tothe right of way of interest.

The integrated handheld device 800 also serves as a personal navigationaid for the user. The handheld unit 800 may carry a map of the right ofway to be inspected in the field and displays/tracks the user's GPSposition continuously with respect to the right of way being inspected.The integrated handheld device 800 also carries a digital camera (notshown) with which the user can take a picture of the vegetationviolating the specified clearance criteria. Other objects of interest tothe user may be documented as well. All photographs taken aregeo-referenced to the GPS location of the user at the time thephotograph is taken.

The integrated handheld device 800 may also include a cellularcommunications module in order to access real time kinematics (“RTK”)survey networks that are used to improve the GPS location computations.Although it is not necessary to access available RTK networks for eachand every use of the handheld unit 800, the RTK network access issufficient to improve the accuracy of the GPS location determinations asmay be required by the user of the handheld instrument. Additionally,the cellular communications capability may be used to transfer picturesand/or data back from the field to a home base of operations.

The laser range finder 806 includes a pistol grip 814 and integratedtrigger 816 for firing the laser. The integrated trigger 820 fires thepivoting laser rangefinder 806 and results in less movement of the laserrangefinder 806 during the firing process than does a pushbutton firingmechanism. The laser range finder 806 is attached to the non-magneticstaff 802 using a clamp 818 capable of swinging through a vertical arcwhile remaining fixed otherwise (e.g., it cannot maneuver/swivel througha horizontal angle or arc). The laser range finder 806 is used to makemultiple measurements from the user's position to the position of thevegetation point of interest or other object of interest. The positiondata may include range to target, azimuth from north, and declinationangle from the user's eye position to the target position.

The handheld computer 808 is clamped into an adjustable mounting bracket820 so that its horizontal and vertical orientation may be changed tosuit the working conditions of the user. The handheld computer 808 mayinclude a personal GPS navigator and a right of way map provider. Thehandheld computer 808 may include software that performs vegetationviolation assessment/analysis, vegetation violation reporting, storageof data representing vegetation violation. The computer 808 may alsoinclude an interface for communication of the data and a camera forimage documentation of the vegetation violation. The laser pointer 810allows the user to designate the vegetation violations to a spotter whois responsible for flagging the violation for further clearing action.

FIG. 9A shows a map display 900 that may be shown on the display screen812 of the handheld computer 808. The display screen 812 in this exampleis configured to display graphics to use the handheld device 800 as apersonal navigation tool by being a GPS guide to the area or target ofinterest. The display screen 812 may show the GPS location of the userrelative to the map display 900 showing a right of way relative tovegetation/objects that have been identified/located as violations ofthe specified clearance criteria. In this example, the right of way isdefined by boundary lines 902. The conductors are represented by lines904. Mapped vegetation 906 is in violation of the clearance criteria andis shown graphically relative to the right of way 900 and the conductors904. The display screen 812 may document or map the results of theuser's actions to identify and locate clearance violations. Mappedstructures 908 are displayed along with identification numbers.

The map display 900 includes a map control bar 910 which includescontrols such as zoom in, zoom out, information, and view. The display812 also includes a results tab 912, a detail tab 914 and a position tab916 that allows the user to navigate between different displays. In thisexample, the position tab 916 is selected to display the map display900.

The user locates his position in the area of interest within the rightof way 902 by monitoring the GPS location on the display screen 812.While in position, the user may use the handheld device 800 toaccomplish several tasks. The user may verify the results of a previousanalysis such as by taking measurements of previously identified/locatedvegetation violations to ensure that none were missed. The user mayaudit the results of a clearing/trimming action such as by visiting thelocations of known violations to see that they were in fact removed bythe clearing action or they were not removed. The user may perform a newinspection/assessment of the vegetation in the right of way. Usually,this work would be performed after considerable time had passed and thevegetation had time to grow back to become a new violation.

With reference to FIG. 8, while in position, the user may scan thevegetation before him to select a piece of vegetation that appears to bea threat to the electrical conductor. The user aims the laser rangefinder 806 at the selected piece of suspect vegetation and squeezes thetrigger once to measure the distance from the laser range finder to thetarget, the azimuth from north to the target, and the declination anglefrom the forester's eye to the target. The user may reference the map900 on the display screen 812 to see what status(violation/no-violation) has been determined by the analysis method forthe single-shot measurement. Additional information for the particular“shot” may be observed by advancing through various screens of thedisplay after each “shot.” This process may be repeated for each pieceof suspect vegetation identified.

After each shot of the laser range finder 806, the handheld computer 808updates the display screen 812 to display a symbol mapped to the remotelocation of the target and indicating the status of the assessment(violation/no-violation). In this example, the map display 900 in FIG.9A shows four locations 920, 922, 924 and 926 which have been shot andtheir respective status. It is not necessary that the user look at thedisplay screen 812 after each shot since the status of the shot isdisplayed by the appropriate symbols to indicate violation status. Thelaser range finder 806 provides user feedback (audible and visual) toindicate that a “shot” was made successfully or not. In fact, based onreceipt of the feedback from the laser range finder 806, the user maycontinue to take multiple shots, one right behind the other, proceedingdown the right of way or out beyond the right of way boundary as may berequired.

After each shot of the laser range finder 806, the software of thehandheld computer 808 determines the remote location of the target pointeither inside the right of way or outside the right of way and analyzesthe remote target point (using the clearance surfaces) to determinewhether or not the target violates the clearance criteria for themultiple conductor operating conditions being analyzed. The analysisperformed may include grow-in and/or fall-in violations. The computer808 analyzes the remote target point to determine whether or not thevegetation point is a violation of the allowable vegetation height inthe right of way and/or edge-growth/encroachment clearance criteria. Thevarious criteria are user defined and selected. The computer 808 alsostores the results to an internal storage device.

FIG. 9B is a view of the display 812 in FIG. 8 showing a result display930 which includes the analysis of the captured vegetation point forconductor vegetation grow in analysis. In this example, the user hasrequested analysis relating to grow-in violations and has selected thedetail tab 914. The display includes an analysis column 932 and a resultcolumn 934. The analysis column 932 includes the user defined clearancecriteria risk levels which are shown in criteria fields 940. Thecriteria fields 940 in this example may include up to four risk levelssuch as planned criteria, minimum fall tree, action (not shown) andurgent (not shown). Each of the criteria field may have up to three userselected conductor operating conditions as shown in the conditionsfields 942. In this example, the user has selected three differentconditions expressed in the conditions fields 942, an as measuredcondition, a maximum sag condition and a maximum blow out condition. Theresults of the analysis for each of the respective criteria andconditions are shown in the result column 934. In this example, thevegetation object violates the clearance surface according to the plancriteria so the as measured condition under the risk level-plan field isindicated as a failure (a violation). The max sag field and the maxblowout criteria under the as measured condition are indicated as NA asthey are not applicable to this analysis. In this example, the analysisis not extended to the other risk levels, and thus these conditions arealso indicated as NA.

FIG. 9C is a view of the display 812 in FIG. 8 showing a result display960 which includes the analysis of the captured vegetation point for rowvegetation edge growth and height encroachment analysis. In thisexample, the user has requested analysis relating to edge growth andheight violations and has selected the detail tab 914. In this example,the user may select between three different criteria for encroachmentanalysis. The selected criteria are shown in criteria fields 950. Inthis example, the user has selected three risk levels or criteria, aplanned criteria, an action criteria and an urgent criteria. Each of thecriteria may have up to two user selected conditions shown in conditionfields 952 under each criteria. In this example, the two conditions aregrowth height and edge (side growth) encroachment. In this example, thegrowth height for the vegetation object is violated according to theplanned criteria and therefore a fail is indicated. The edgeencroachment assessment is not applicable and therefore is assigned anNA designation in this example. The remaining conditions of theremaining risk criteria also are not applicable and are assigned an NAdesignation in this example.

FIG. 9D is a view of the display 812 in FIG. 8 after the detail tab 954is selected. FIG. 9C shows a detail screen 980 showing the criteria usedto generate the analysis of the captured vegetation for purposes of thegrow in analysis shown in FIG. 9B. The detail screen 980 indicates thecriteria used for the analysis displayed in FIG. 9B. In this example,the method is specified as a radial. Each of the conditions for the risklevels is expressed in feet. Thus, the radial clearance criteria for themaximum sag allowed for the planned criteria is 15 feet, while theradial criteria for the maximum sag allowed for the action risk level is10 feet and the radial criteria for the maximum sag allowed for theurgent risk level is 5 feet. In addition, the criteria is specified formeasurements from the structures such as towers for the conductors. Inthis example, the radial criteria at the structure for the planned risklevel is 15 feet, the radial criteria at the structure for the actionrisk level is 10 feet and the radial criteria at the structure for theurgent risk level is 5 feet. The clearance criteria at mid-span ormaximum sag location may be assigned a different numeric value than atthe structure to reflect an assessment of risk by a user.

After each shot of the laser range finder 806, the handheld computer 808updates the internal storage to store the location and detailed statusof the vegetation point location “shot” for each conductor operatingcondition analyzed. This internally stored data is available (in GISformat) for subsequent uploading to some other more permanent storagemedia upon completion of the field inspection activity in this example.

Upon encountering a vegetation violation, the user may “designate” thelocation of the violation to a “spotter” crew member via the laserpointer 810 who will then “flag” the violation to identify it forfurther clearing action.

In this example, the handheld computer 808 includes a data storage cardthat is a small media device for storing the definitions of thesegmented clearance surfaces previously constructed, the previouslysegmented bare earth coordinate points, and the pertinent clearanceanalysis parameters for each of the multiple conductor operatingconditions to be analyzed. This data is determined by the processdescribed above with reference to FIGS. 1-9. The small physical size ofthe storage card as well as its limited data storage capacity illustratethe effectiveness and efficiency with which the clearance surface datamodeling technique models the entire geometry of the right of way to beanalyzed. Similarly, the memory capacity of the handheld computer 808 islimited and this procedure lends itself to geometric modeling efficiencyand analysis capabilities. Of course, more memory and higher capabilitycomputers may be used for the above described processes.

In this example, one data storage card is capable of handling the entiredata model for a 20 mile to 50 mile electric power transmission right ofway. The data storage card can be used repeatedly for differentrights-of-way by uploading the appropriate data model(s) to the cardprior to carrying the handheld device 800 (with its card or cards) tothe field. The data card in this example may also handle the entire datamodel for a 20 mile to 50 mile electric power transmission right of waywhen at least four different clearance criteria are used to createclearance surfaces for at least three conductor operating conditions.

Thus, the device 800 is capable of using the clearance surface datadetermined as described above to perform all the previously specifiedtypes of clearance analysis types in the field. Specifically, the device800 is portable and lightweight and may be effectively operated by aforester. The use of the device 800 may effectively reduce the fieldinspection crew size that is typically used in the field for detecting,analyzing, identifying, and reporting vegetation violations usingspecific clearance criteria and therefore effectively increase theproductivity of the field inspection crew. The device 800 may use andre-use the previously constructed clearance surface data models over andover again, well into the future, to perform new inspections of thecorridor.

FIG. 10A is a scaled planimetric drawing 1000 of the results of avegetation grow-in/fall-in analysis using the clearance surface methoddescribed above along with pertinent supporting information. The drawing1000 is a two part map of a corridor/right of way 1002 that contains anumber of conductors 1004 in the corridor/right of way. The drawing 1000includes structure locations 1006 with identifying marks/names, right ofway boundaries 1008, ground contours 1010 in elevation above sea level,and clearance surface contours 1012 expressed in height above groundlevel. The clearance surface may be effectively raised or lowered toeffectively simulate vegetation growth in both vertical and horizontaldimensions.

The map 1000 includes the inventory of vegetation violation clusters1014 inside and outside the right of way. The vegetation clusters 1014are numbered to identify the particular span to which they “belong” andto define whether they exist inside or outside the right of wayboundary. The vegetation clusters are bounded by a closed polygon tofacilitate the calculation of the area included in the bounded polygon.Other attributes of the vegetation violation cluster may includeperimeter, centroid location, apparent tree top locations and/or otherrelevant attributes.

FIG. 10B is a scaled planimetric drawing 1020 showing the results of avegetation analysis that determines whether or not the vegetation insidethe boundaries of the right of way/corridor exceeds an allowable heightcriteria and/or whether or not the vegetation along the sides of theboundaries of the right of way encroach (beyond an allowable horizontaldistance criteria) into the right of way (e.g., the vegetation's lateralgrowth, above the allowable height criteria. Identical elements to FIG.10A are labeled with like element numbers in FIG. 10B. FIG. 10B includesvegetations clusters 1020 that violate a height above ground clearancecriteria or a side growth encroachment clearance criteria.

FIGS. 10A and 10B illustrates a report format that can be taken to thefield in hardcopy form, and it illustrates a report format that may beused in electronic form to provide a base for mapping vegetationtype/species and any other of a variety of useful information.

FIG. 11 depicts the “leaning tree problem” Vegetation clearance analysistechniques applied to point coordinate data (LIDAR, or otherwise) mayproduce false positives (violation points that are not actuallyviolations) due to the fact that any single/individual point coordinatecannot be accurately determined to be located on either a leaning treeor a vertically standing tree. A vertically standing tree is assumedwith the absence of confirmation. The leaning tree may not be an actualviolation due to its degree of lean. Currently, it is not possible toautomatically detect and extract individual tree trunks from point cloudcoordinate data. As will be described below, such trees may beidentified via the handheld device 800 in FIG. 8.

Before a violation (hazard) tree is actually cut, a forester identifiesthe tree and physically tags or marks the as a violation/hazard tree tobe cut by the cutting crew. Therefore, the determination of whether ornot a given hazard tree is leaning is left to the forester observing thesituation in the field. In this example, the software in the hand helddevice 800 includes an algorithm for determining whether or not aleaning tree actually does or does not pose a threat to the conductors(e.g., a clearance violation or hazard tree). If the tree is determinedto be a “leaning tree” by a forester in the field, then the forester mayuse the hand held device 800 necessary to determine that the vegetationpoint in question is either a valid violation of the vegetationclearance criteria or a false-positive point to be discarded.

FIG. 11 shows a cross-section of a tree trunk 1100 and the variousdimensions that are used by the mathematical technique performed in thehandheld device 800 to determine whether a violation exists in relationto an electrical conductor 1102. In FIG. 11, point P4 has beendetermined (using the analysis method) to be in violation of thespecified clearance criteria relative to point P1 which represents apoint on the electrical conductor 1102. Therefore, the distance betweenpoint P4 and point P3 (the point on the ground about which the fallingtree rotates when it falls) represents the tree's height which issufficient to violate the radial clearance criteria (R) when the fallingtree passes through the vertical angle beta (measured above thehorizontal plane). For violation point P4, the vertical angle Θ(measured from the horizontal plane) represents the maximum allowable“lean angle.” It is apparent that vegetation points (e.g., point P6 onthe leaning tree 1100) directly below point P4 and having an apparentlean angle of chi above the horizontal would not have a tree heightsufficient to cause point P6 to be a violation of the clearancecriteria. However, it is also apparent that vegetation points (e.g.,point P5 on the leaning tree) directly above point P4 and having a leanangle of Ψ above the horizontal would have a tree height sufficient tocause point P5 to be a violation of the clearance criteria. Therefore,the determination of the apparent lean angle is both necessary andsufficient to determine whether or not the vegetation point at issuewould or would not be in violation of the clearance criteria. Using thehandheld device 800, a forester may determine the apparent lean angle ofthe leaning tree 1100 and thus determine if the vegetation point atissue is or is not in violation of the specified clearance criteria.

The forester's procedure for making this determination requires twoshots of the laser range finder 806. The forester stands under theelectrical conductor 1102 at a point closest to the apparent violatingvegetation point P4 (tree top) while facing in a direction perpendicularto the conductor and using the laser range finder 806 located at pointP2 to shoot the apparent violating vegetation point which is the top ofthe tree 1100 in this example. This determines via a preselected laserrange finder function the horizontal distance (u) from the conductor andthe laser range finder 806 to the top of tree (either point P4, P5, orP6) and the vertical distance (Q) from the laser range finder 806 atpoint P2 and the top of the tree (either point P4, P5, or P6).

The forester then relocates (if necessary) and stands under theelectrical conductor 1102 at a point closest to the base of the leaningtree (point P3) while facing in a direction perpendicular to theconductor and using the laser range finder 806 now located at point P2′to shoot the base of the leaning tree (point P3), thus determining viathe preselected laser range finder function the horizontal distance fromthe conductor to the base of the leaning tree (point P3) and thevertical distance (c) from the laser range finder 806 at point P2′ andthe base of the leaning tree (point P3). In this example, the base andthe top of the tree 1100 (points P3 and P4) are in the same plane thatperpendicular to the vertical plane and therefore points P2 and P2′ arein the same location. If the tree 1100 were leaning at an angle suchthat the base (point P3) was either proximal or distal to the viewer ofFIG. 11 relative to the top at point P4, the forester would have torelocate toward or away from point P2 to shoot the base of the learningtree 1100.

The algorithm will make a determination based on the data whether thetree 1100 is a violation and will display whether the vegetation point(P4) is or is not a violation of the clearance criteria on the displayscreen 812. The algorithm determined if the apparent leaning tree height(T) is greater than the difference (a−R). That is, conservatively, aviolation occurs if [T=>(a−R)], where R=Radial Clearance Criteria,L=SQRT((a*a)+(c*c)), {SQRT is the Square Root function},S=SQRT((u*u)+(Q*Q)), and T=SQRT((S*S)−(L*L)).

Additionally, if [T=>(a−R)], a useful maximum allowable apparent leanangle (Θ) is determined (and displayed) by determining v=a−u and Θ=ACOS(v/T), where A COS is the arc-cosine function and any vegetationpoints located directly above point P4 (e.g., Ψ>Θ) are to be designatedas violations of the radial clearance criteria while any vegetationpoints located directly below point P5 (e.g., χ<Θ) are to be designatedas non-violations of the radial clearance criteria.

As shown in FIG. 13, the computer to determine the clearance data andthe computer 808 may include a central processing unit (CPU), controlleror processor 100, a memory 102, and an interface system 104 which arecoupled together by a bus 106 or other link, although other numbers andtypes of each of the components and other configurations and locationsfor the components can be used. The processors in the computersdescribed herein may execute a program of stored instructions for one ormore aspects of the methods and systems as described herein, includingfor determining regions of clearance violations, although the processorcould execute other types of programmed instructions. The memory maystore these programmed instructions for one or more aspects of themethods and systems as described herein, including the method fordetermining regions of clearance violations, although some or all of theprogrammed instructions could be stored and/or executed elsewhere. Avariety of different types of memory storage devices, such as a randomaccess memory (RAM) or a read only memory (ROM) in the system or afloppy disk, hard disk, CD ROM, DVD ROM, or other computer readablemedium which is read from and/or written to by a magnetic, optical, orother reading and/or writing system that is coupled to the processor,may be used for the memory. The user input device 108 may comprise acomputer keyboard and a computer mouse, although other types and numbersof user input devices may be used. A display 110 may comprise a computerdisplay screen, such as a CRT or LCD screen by way of example only,although other types and numbers of displays could be used.

Although an example of the computers are described and illustratedherein in connection with FIGS. 1-7, each of the computers could beimplemented on any suitable computer system or computing device. It isto be understood that the example devices and systems are for exemplarypurposes, as many variations of the specific hardware and software usedto implement the methods described herein, as will be appreciated bythose skilled in the relevant art(s).

Furthermore, each of the devices described herein may be convenientlyimplemented using one or more general purpose computer systems,microprocessors, digital signal processors, micro-controllers,application specific integrated circuits (ASIC), programmable logicdevices (PLD), field programmable logic devices (FPLD), fieldprogrammable gate arrays (FPGA) and the like, programmed according tothe teachings as described and illustrated herein, as will beappreciated by those skilled in the computer, software and networkingarts.

In addition, two or more computing systems or devices may be substitutedfor any one of the computers described herein. Accordingly, principlesand advantages of distributed processing, such as redundancy,replication, and the like, also can be implemented, as desired, toincrease the robustness and performance of computers described herein.The computers may also be implemented on a computer system or systemsthat extend across any network environment using any suitable interfacemechanisms and communications technologies including, for exampletelecommunications in any suitable form (e.g., voice, modem, and thelike), Public Switched Telephone Network (PSTNs), Packet Data Networks(PDNs), the Internet, intranets, a combination thereof, and the like.

The operation of the example determination of clearance surfaces andwhether objects violate the clearances, will now be described withreference to FIGS. 1-7 in conjunction with the flow diagrams shown inFIG. 12. The flow diagram in FIG. 12 is representative of examplemachine readable instructions for implementing determination ofclearance surfaces and whether objects violate the clearances. In thisexample, the machine readable instructions comprise an algorithm forexecution by: (a) a processor, (b) a controller, and/or (c) one or moreother suitable processing device(s). The algorithm may be embodied insoftware stored on tangible media such as, for example, a flash memory,a CD-ROM, a floppy disk, a hard drive, a digital video (versatile) disk(DVD), or other memory devices, but persons of ordinary skill in the artwill readily appreciate that the entire algorithm and/or parts thereofcould alternatively be executed by a device other than a processorand/or embodied in firmware or dedicated hardware in a well known manner(e.g., it may be implemented by an application specific integratedcircuit (ASIC), a programmable logic device (PLD), a field programmablelogic device (FPLD), a field programmable gate array (FPGA), discretelogic, etc.). For example, any or all of the components of thedetermination of clearance surfaces and whether objects violate theclearances could be implemented by software, hardware, and/or firmware.Also, some or all of the machine readable instructions represented bythe flowchart of FIG. 12 may be implemented manually. Further, althoughthe example algorithm is described with reference to the flowchartillustrated in FIG. 12, persons of ordinary skill in the art willreadily appreciate that many other methods of implementing the examplemachine readable instructions may alternatively be used. For example,the order of execution of the blocks may be changed, and/or some of theblocks described may be changed, eliminated, or combined.

In FIG. 12, the centerline of the right of way is defined (1200). Inthis example, the right of way includes various structures such aselectrical towers which define spans between the towers. Thus, catenarycurves of the conductors between the towers are determined (1202).Vegetation coordinate points are determined from the cloud of image datafrom a scene (1204). The bare earth coordinates are then determined fromthe cloud of image data from the scene (1206).

A first 3-D clearance surface segment is constructed between a firstspan using the determined right of way, catenary curve and the bareearth coordinates (1208). The bare earth coordinates are then segmentedfor the span (1210). The process then determines whether there areadditional spans (1212). If there are remaining spans, the process thenloops back to 1208 to construct the next clearance surface segment.

After all of the surface segments are constructed (1212), the vegetationpoints are classified as a violation of the clearance curves or not bylocating the vegetation that violates the clearance curves (1214). Theviolations results and classification analysis is then stored (1216).

Having thus described the basic concepts, it will be rather apparent tothose skilled in the art that the foregoing detailed disclosure isintended to be presented by way of example only, and is not limiting.Various alterations, improvements, and modifications will occur and areintended to those skilled in the art, though not expressly statedherein. These alterations, improvements, and modifications are intendedto be suggested hereby, and are within the spirit and scope of theexamples. Additionally, the recited order of processing elements orsequences, or the use of numbers, letters, or other designationstherefore, is not intended to limit the claimed processes to any orderexcept as may be specified in the claims. Accordingly, the invention islimited only by the following claims and equivalents thereto.

What is claimed is:
 1. A method for determining clearance violations inan area, the method comprising: storing a clearance surface data modelof a three-dimensional topographic boundary area including terrainincluding a clearance surface between a first object and a second objectin a storage device at a first time period; receiving data of apotential obstruction object in the three-dimensional topographical areaat a second time period after the first time period; and determiningwhether the potential obstruction object is a violation of the clearancesurface based on the stored clearance surface data model via acontroller.
 2. The method of claim 1, further comprising: producing amap of the area including the clearance surface; and displaying a threedimensional topographical map showing the potential obstruction objecton the terrain on an electronic display.
 3. The method of claim 2,wherein the potential obstruction object is displayed on the threedimensional topographical map.
 4. The method of claim 2, wherein theclearance surface includes contour lines.
 5. The method of claim 1,wherein the data of the potential obstruction object is LIDAR data ofthe area.
 6. The method of claim 5, wherein the determination of aviolation includes evaluating the LIDAR data on a point by point basisto determine whether a point exists on or above the clearance surface.7. The method of claim 1, wherein the stored clearance surface datamodel is obtained by locating waypoints to define a centerline and theboundary area and constructing the clearance surface within the boundaryarea between the first and second object determined from the location ofthe first and second object and clearance criteria.
 8. The method ofclaim 7, wherein the clearance criteria includes radial criteria, NESCcriteria, or constant slope criteria.
 9. The method of claim 1, whereinthe potential obstruction includes vegetation in the area, wherein thedata of the potential obstruction object includes vegetation coordinatepoints in the area.
 10. The method of claim 1, wherein the first andsecond objects are consecutive supporting structures forming a span inthe boundary area, and wherein the clearance surface includes aclearance surface segment constructed for the span.
 11. The method ofclaim 10, wherein the clearance surface segment preserves the entiregeometrical properties of operating facilities within the boundary arealength, the geometric properties including structures, conductorcatenary curves, and conductor attachment points.
 12. The method ofclaim 1, wherein the clearance surface data model includes clearancesurface segments, clearance surface analysis results, a GIS map of theboundary area, and a digital terrain surface.
 13. The method of claim 1,wherein the clearance surface data model includes data representingutility facilities in the area.
 14. The method of claim 1, wherein theclearance surface data model is constructed for at least one of afacility operating condition or a construction method.
 15. The method ofclaim 1, wherein the data of the potential obstruction object isobtained from a portable hand held device recording the location of thepotential obstruction object in the area.
 16. A system to determine aviolation of a clearance surface for boundary area, the systemcomprising: a storage device storing a clearance surface data model of athree-dimensional topographic boundary area including a clearancesurface between a first and a second object at a first time period; aninput device for receiving data of a potential obstruction object in thethree-dimensional topographical area at a second time period after thefirst time period; a processor determining whether the potentialobstruction object is a violation of the right of way based on thestored clearance surface data model.
 17. The system of claim 16 furthercomprising a display coupled to the processor, wherein the processorcreates a three-dimensional map of the boundary area including theclearance surface and the potential obstruction object.
 18. The systemof claim 16, wherein the storage device, input device and processor arein a portable handheld device.
 19. The system of claim 16, wherein theinput device is a receiver for receiving LIDAR data of the potentialobstruction object.